1. Field of the Invention
This invention relates to an electric control device and, more particularly, it pertains to a thermally responsive overload relay.
2. Description of the Prior Art
A thermal overload relay is a bimetallic device which provides motor protection for running and stalled rotor overloads. A strip bimetal in the overload relay is electrically heated by heater elements which carry the motor currents. Excess heat is generated in the heater elements by an overloaded motor. The bimetals deflect to thermally open the normally closed contact, thereby opening a coil circuit of a magnetic contactor which disconnects the overloaded motor from the line. Thereafter the relay may be reset by pressing and releasing a reset rod.
Thermal overload relays of the type used to protect an electric motor are known in the art and disclosed in U.S. Pat. Nos. 3,265,831; 3,792,401; 3,842,383; and 4,047,140. Economic factors such as cost of materials in competing products often require a consideration of cost-cutting measures without sacrificing quality. Some prior existing overload relays having reliability and endurance have been too costly and awkward when replacing worn-out or broken parts.